Polymorphs of Cocrystals of p-Coumaric Acid:Nicotinamide

ABSTRACT

Polymorphs, Forms II and III, of cocrystals of p-coumaric acid and nicotinamide in a 1:1 molar ratio. Pharmaceutical compositions containing Forms II or III, processes for making such forms, and methods of treatment with such Forms.

This application claims the benefit of priority to U.S. ProvisionalApplication No. 61/935,570, filed on Feb. 4, 2014, the entire contentsof which are incorporated by reference herein.

The invention relates to polymorphs of cocrystals of p-coumaric acid andnicotinamide, pharmaceutical compositions comprising the polymorphs ofthe novel cocrystals, methods of making the polymorphs of the novelcocrystals, and methods of treatment with polymorphs of the novelcocrystals.

BACKGROUND

P-coumaric acid is a phytochemical and nutraceutical and is commonlyfound in various edible plants such as peanuts, tomatoes, and carrots.Promising pharmacokinetic studies with p-coumaric acid have shown it tohave a positive response in protection against colon cancer on culturedmammalian cells. Other studies have shown it to have anti-inflammatoryand antioxidant properties in animals. Nicotinamide is the amide ofnicotinic acid and is a water-soluble vitamin. Nicotinamide hasanti-inflammatory properties and is used in the treatment of acne.

The structures of p-coumaric acid and nicotinamide are shown below:

Cocrystals of p-coumaric acid have previously been published. Forexample, cocrystals with caffeine and theophylline have previously beendescribed (Cryst. Eng. Comm. 2011, 13 611-19). Likewise, cocrystalscontaining nicotinamide have been reported. In addition, a 1:1 cocrystalof p-coumaric acid:nicotinamide has been prepared by the inventors. Thecocrystals disclosed herein are polymorphs of that cocrystal.

A cocrystal of a compound is a distinct chemical composition between thecompound and coformer, and generally possesses distinct crystallographicand spectroscopic properties when compared to those of the compound andcoformer individually. A coformer is also a compound and is oftenreferred to as a “guest”. The compound which is not the coformer isoften referred to as the “host.” Unlike salts, which possess a neutralnet charge, but which are comprised of charge-balanced components,cocrystals are comprised of neutral species. Thus, unlike a salt, onecannot determine the stoichiometry of a cocrystal based on chargebalance. Indeed, one can often obtain cocrystals having molar ratios ofcompound to coformer of greater than or less than 1:1. The molar ratioof the components is a generally unpredictable feature of a cocrystal.

Cocrystals have the potential to alter physicochemical properties. Morespecifically, cocrystals have been reported to alter aqueous solubilityand/or dissolution rates, increase stability with respect to relativehumidity, and improve bioavailability of active pharmaceuticalingredients with respect to other cocrystals of such ingredients. Thecoformer, or guest, is often varied or selected for purposes of alteringsuch properties.

The chemical composition of a cocrystal, including the molarrelationship between the coformer and the compound (such as an API) canbe determined by single crystal x-ray analysis. Where such an analysisis not available, often solution-state proton NMR is used to verifycomposition and identify molar ratio.

Cocrystal formation may be further confirmed by comparing solid-stateanalytical data of the starting materials with the correspondinganalytical method collected of the cocrystal. Data from a cocrystal willbe represented by an analytical response that is not simply a linearsuperposition of the starting materials. For example, x-ray powderdiffraction (XRPD) may be used for such comparison and the XRPD patternof a cocrystal will differ from that of a physical mixture of thestarting materials. Single crystal studies can confirm solid-statestructure. In a cocrystal, the compound and the coformers each possessunique lattice positions within the unit cell of the crystal lattice.Additionally, indexing may be used to confirm the presence of a singlephase.

A single crystal structure is not necessary to characterize a cocrystal.Other solid-state analytical techniques may be used to characterizecocrystals. Crystallographic and spectroscopic properties of cocrystalscan be analyzed with XRPD, Raman spectroscopy infrared spectroscopy, andsolid-state ¹³C NMR spectroscopy, among other techniques. Cocrystalsoften also exhibit distinct thermal behavior compared with other formsof the corresponding compound. Thermal behavior may be analyzed by suchtechniques as capillary melting point, thermogravimetric analysis (TGA),and differential scanning calorimetry (DSC) to name a few. Thesetechniques can be used to identify and characterize the cocrystals.

For example, the entire XRPD pattern output from a diffractometer may beused to characterize a cocrystal. A smaller subset of such data,however, may also be suitable for characterizing a cocrystal. Forexample, a collection of one or more peaks from such a pattern may beused to characterize a cocrystal. Indeed, even a single XRPD peak may beused to characterize a cocrystal. Similarly, subsets of spectra of othertechniques may be used alone or in combination with other analyticaldata to characterize cocrystals. In such examples of characterization asprovided herein, in addition to the x-ray peak data, one also is able toprovide the identity of the guest and host of the cocrystal and, often,their respective molar ratio as part of the characterization.

An XRPD pattern is an x-y graph with ° 2θ (diffraction angle) on thex-axis and intensity on the y-axis. These are the peaks which may beused to characterize a cocrystal. The peaks are usually represented andreferred to by their position on the x-axis rather than the intensity ofpeaks on the y-axis because peak intensity can be particularly sensitiveto sample orientation (see Pharmaceutical Analysis, Lee & Web, pp.255-257 (2003)). Thus, intensity is not typically used by those skilledin the pharmaceutical arts to characterize cocrystals.

As with any data measurement, there is variability in x-ray powderdiffraction data. In addition to the variability in peak intensity,there is also variability in the position of peaks on the x-axis. Thisvariability can, however, typically be accounted for when reporting thepositions of peaks for purposes of characterization. Such variability inthe position of peaks along the x-axis derives from several sources. Onecomes from sample preparation. Samples of the same crystalline material,prepared under different conditions may yield slightly differentdiffractograms. Factors such as particle size, moisture content, solventcontent, and orientation may all affect how a sample diffracts x-rays.Another source of variability comes from instrument parameters.Different x-ray instruments operate using different parameters and thesemay lead to slightly different diffraction patterns from the samecrystalline cocrystal. Likewise, different software packages processx-ray data differently and this also leads to variability. These andother sources of variability are known to those of ordinary skill in thepharmaceutical arts.

Due to such sources of variability, it is common to recite x-raydiffraction peaks using the word “about” prior to the peak value in ° 2θwhich presents the data to within 0.1 or 0.2 ° 2θ of the stated peakvalue depending on the circumstances. All x-ray powder diffraction peakscited herein are reported with a variability on the order of 0.2 ° 2θand are intended to be reported with such a variability wheneverdisclosed herein whether the word “about” is present or not.

Thermal methods are another typical technique to characterizecocrystals. Different cocrystals of the same compound often melt atdifferent temperatures. Variability also exists in thermal measurementsand may also be indicative of sample purity. Melting point, such asmeasured by differential scanning calorimetry (DSC) and thermalmicroscopy, alone or in combination with techniques such as x-ray powderdiffraction, may be used to characterize cocrystals.

As with any analytical technique, melting point determinations are alsosubject to variability. Common sources of variability, in addition toinstrumental variability, are due to colligative properties such as thepresence of other cocrystals or other impurities within a sample whosemelting point is being measured.

SUMMARY

In one aspect of the invention, a cocrystal of p-coumaric acid tonicotinamide in a 1:1 molar ratio is disclosed referred to as Form II.In a further aspect of the invention, another cocrystal of p-coumaricacid to nicotinamide in a molar ratio of 1:1 is disclosed and isreferred to as Form III. In further aspects, pharmaceutical compositionscomprising one or both of the cocrystals described herein are described.In yet further aspects, methods of treating conditions treatable byadministration of the cocrystals described herein are disclosed as areprocesses for making such cocrystals.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an XRPD pattern of p-coumaric acid.

FIG. 2 is an XRPD pattern of nicotinamide.

FIG. 3 is an XRPD pattern of Form II.

FIG. 4 is an XRPD pattern of Form III (with minor component being FormII).

FIG. 5 is a DSC Thermogram of Form II.

FIG. 6 is a DSC Thermogram of Form III (with a minor component beingForm II)

DESCRIPTION

The XRPD pattern corresponding to the p-coumaric acid starting materialused herein is in FIG. 1. The XRPD pattern of the nicotinamide startingmaterial is in FIG. 2. The XRPD pattern for the resulting Form II is inFIG. 3.

As can be readily determined, the XPRD pattern of FIGS. 3 and 4respectively differ from those of FIGS. 1 and 2, and, therefore, FormsII and III not merely a linear superposition of the patterns. Rather,these data prove that the cocrystals of Forms II and III are notmixtures of starting materials but are distinct compositions of matter.

In one embodiment of the invention, Form II of a cocrystal of p-coumaricacid to nicotinamide in a molar ratio of 1:1 is disclosed. In anotherembodiment of the invention, Form III of a cocrystal of p-coumaric acidto nicotinamide in a molar ratio of 1:1 is disclosed. In additionalembodiments, pharmaceutical compositions of Forms II, III, or both aredescribed herein. Other embodiments include processes for making FormsII or III and still further embodiments include methods of treatingdiseases such as inflammation with Forms II or III or both.

Form I of a cocrystal of p-coumaric acid to nicotinamide in a molarratio of 1:1 has previously been disclosed and claimed in US2014/0073674. Forms I, II, and III of the 1:1 cocrystal of p-coumaricacid and nicotinamide are polymorphs of one another. Polymorphs of acompound share the same chemical formula but differ in crystallinestructure. The differences in chemical structure may be identified byreference to any one of a number of analytical techniques. Thesetechniques may be used to distinguish polymorphs from one another and,therefore, may be used to characterize the polymorphs.

The different polymorphic forms of the 1:1 cocrystal of p-coumaricacid:nicotinamide may be characterized by a number of differentanalytical techniques. For example, Form I may be distinguished fromboth Forms II and III by melting point alone. The onset melting point ofForm I as measured by DSC and confirmed by thermomicroscopy as disclosedherein is 154° C. whereas Forms II and III under the same conditionsmelt at about 158° C. and about 160° C. respectively. Further, Form Iexhibits peaks in the x-ray XRPD pattern, as measured under similarexperimental conditions as Forms II and III, at about 5.9 and 11.8degrees two theta. Neither Form II nor Form III have peaks withintypical experimental variation of those two peaks. Thus, either one ofthose peaks, together with or separate from melt onset as measuredherein at about 154° C. can distinguish Form I from Forms II or III.

Forms II and III may be further distinguished from each other by boththermal measurements and by XRPD peaks. The melting point differences ofabout 158° C. and about 160° C. for Forms II and III respectively aresufficient to characterize the forms. These melting points aredetermined by a combination of DSC and thermomicroscopy. For example,FIG. 5, a DSC thermogram of Form II, illustrates an endotherm onsetoccurring at about 158° C. Thermomicroscopy confirms that this endothermis a melt. FIG. 6 is a DSC thermogram of Form III (with a minorcomponent of Form II), which by DSC and thermomicroscopy shows anendotherm onset which is a melt occurring at about 160° C.

The forms may also be characterized by XRPD. For example, as seen inFIGS. 3 and 4, Form II exhibits a peak in its XRPD pattern, as set forthherein, at about 26.3 ° 2θ whereas Form III exhibits a peak at about25.8 ° 2θ. Either single peak alone, or in combination with the onsetmelting temperature, suffices to characterize each of Form II and FormIII. In addition, Form II exhibits two peaks at between about 15.4 ° 2θand 16.0 ° 2θ (about 15.6 ° 2θ and 15.8 ° 2θ) degrees two theta whereasForm III only has one peak in that range (about 15.7 ° 2θ). Thus, thepresence of only one peak between about 15.4 ° 2θ and about 16.0 ° 2θalone characterizes Form III. The presence of a single peak betweenabout 15.4 ° 2θ and about 16.0 ° 2θ together with a peak at about 25.8 °2θ and/or the melting onset of about 160° C. may be used to characterizeForm III. By comparison, the presence of two peaks between about 15.4 °2θ and about 16.0 ° 2θ may be used to characterize Form II or these twopeaks in combination with a peak at about 26.3 ° 2θ and/or a meltingonset of 158° C. may be used to characterize Form II.

By “peak” as used herein what is meant is a signal that is not noise andwhich represents a reflection in the x-ray powder diffraction pattern.Those of ordinary skill in the art recognize that some peaks aresusceptible to preferred orientation or particle statistical affects.The fact that a peak may not be visible due to these affects does notmean the peak is not present in the material. Thus, to rule out thepresence of a peak other than due to such artifacts, it may be necessaryto run replicate samples of the materials analyzed.

This invention also relates to pharmaceutical compositions containingForm II or Form II of the present invention. These compositions can beutilized to achieve the desired pharmacological effect by administrationto a patient in need thereof including, treatment of acne or otherinflammation conditions. A patient, for the purpose of this invention,is a mammal, including a human, in need of treatment for the particularcondition or disease including, but not limited to, acne or otherinflammation conditions. Therefore, the present invention includespharmaceutical compositions which are comprised of at least onepharmaceutically acceptable carrier and one or more of Form II or FormIII of the present invention. A pharmaceutically acceptable carrier isany carrier which is relatively non-toxic and innocuous to a patient atconcentrations consistent with effective activity of the activeingredient so that any side effects ascribable to the carrier do notvitiate the beneficial effects of the active ingredient. Apharmaceutically effective amount of compound is that amount whichproduces a result or exerts an influence on the particular conditionbeing treated. The compound of Form II or Form III or both of thepresent invention can be administered with pharmaceutically-acceptablecarriers well known in the art using any effective conventional dosageunit forms, including immediate, slow and timed release preparations,orally, parenterally, topically, nasally, ophthalmically, optically,sublingually, rectally, vaginally, and the like.

EXAMPLES

All chemicals were obtained from commercial sources and used withoutfurther purification.

Patterns were collected using a PANalytical X'Pert Pro MPD X-raydiffractometer. An incident beam of Cu radiation was produced using anOptix long, fine-focus source. An elliptically graded multilayer mirrorwas used to focus Cu Kα X-rays through the specimen and onto thedetector. The sample was prepared by sandwiching a portion of the solidsbetween 3-μm thick films and analyzing in transmission geometry. Abeam-stop, short antiscatter extension, and an antiscatter knife edgewere used to minimize the background generated by air. Soller slits forthe incident and diffracted beams were used to minimize broadening fromaxial divergence. PANalytical data were collected using a scanningposition-sensitive detector (X'Celerator) located 240 mm from thespecimen and Data Collector software v. 2.2b. Prior to the analysis, asilicon specimen (NIST SRM 640c or 640d) was analyzed to verify the Si111 peak position.

Solution ¹H NMR spectra were acquired at ambient temperature with aVarian^(UNITY) INOVA-400 spectrometer at a ¹H Larmor frequency of399.796 or 399.798 MHz. Each sample was dissolved in DMSO-d₆ containingtetramethylsilane (TMS). The spectra were acquired with the followingparameters: 6-9 μs ¹H pulse width; 2.50 or 5.00 second acquisition time;5.00 or 2.50 second delay between scans; 6400 or 7000 Hz spectral width;31998, 35000, or 64000 data points; and 40 co-added scans. Each freeinduction decay (FID) was processed with 64000, 131072, or 262144 pointsand an exponential line broadening factor of 0.2 Hz to improve thesignal-to-noise ratio. The spectra were referenced to internal TMS at0.0 ppm. Stoichiometry was confirmed for all cocrystals by ¹H NMRspectroscopy, and only minor amounts of residual organic solvents werepresent based on the spectra for each cocrystal. The samples were notvacuum dried prior to characterization, which would leave residualprocess solvents.

DSC was performed using a TA Instruments Q2000 differential scanningcalorimeter. Temperature calibration was performed using NIST-traceableindium metal. Each sample was placed into an aluminum DSC pan or a Tzeropan, covered with a lid, the lid was crimped, and the weight wasaccurately recorded. A weighed aluminum pan configured as the sample panwas placed on the reference side of the cell. Each sample was heatedusing a heating rate of 10° C. per minute from either −30° C. or 25° C.up to 250° C.

Thermomicroscopy was performed using a Linkam hot stage (FTIR 600)mounted on a Leica DM LP microscope equipped with a SPOT Insight™ colordigital camera. The sample was placed on a cover glass with anothercover glass placed on top. As the stage was heated, each sample wasvisually observed using a 20×0.40 numerical aperture long workingdistance objective with crossed polarizers and a first order redcompensator. Images were captured using SPOT software (v. 4.5.9).Temperature calibrations were performed using USP melting pointstandards.

Example 1 Form II Preparation

Weighed amounts of p-coumaric acid (304.0 mg) and nicotinamide (226.1mg) were added to a clean vial in a 1:1 molar ratio. Tetrahydrofuran (20mL) was added with sonication, resulting in a clear solution. Thesolution was uncapped and covered with perforated aluminum foil for slowevaporation at ambient conditions. After approximately 2 weeks, thesample contained solids with a very small amount of solvent remaining.The solids were collected by vacuum filtration and washed withtetrahydrofuran on the filter. Other crystallization techniques thatproduced Form II include cooling, evaporation, vapor diffusion, andslurrying with one component in molar excess, all in a variety ofsolvents such as ethyl acetate, p-dioxane, 2-propanol, and/or methylethyl ketone. An x-ray powder diffractogram of a sample made accordingto Example 1 can be found in FIG. 3.

Example 2 Form III Preparation

Single crystals of Form III were produced from a vapor diffusionexperiment. A bulk solution of p-coumaric acid (102.7 mg, 0.6 mmol) andnicotinamide (76.6 mg, 0.6 mmol) in a 1:1 molar ratio was prepared inethanol (3 mL). A small amount of this solution (550 μL) was added to a1-dram vial, which was placed inside a 20-mL vial containingnitromethane (2 mL). The 20-mL vial was capped for vapor diffusion atambient conditions. After 3 weeks, single crystals of Form III wereharvested, although analysis of the solids by XRPD indicated concomitantcrystallization of Form III and Form II. While multiple crystallizationtechniques, such as cooling, evaporation, and vapor diffusion, utilizinga variety of solvents, produced mixtures of Form III with Form II and/orForm I, only one slow evaporation experiment in ethanol yielded Form IIIprimarily in a single phase with only a minor amount of Form II presentby XRPD. An x-ray powder diffractogram of Form III with a minor amountof Form II is present in FIG. 4. A single crystal structure solution wasperformed on Form III with a summary of the results to be found inTable 1. A calculated XRPD pattern was generated on the single crystaldata represented in Table 1 and was compared with an experimentalpattern of Form III prepared by an ethanol slow evaporation technique.In the experiment corresponding to that slow evaporation technique,p-coumaric acid (99.9 mg) was combined with nicotinamide (76.1 mg) andthe mixture was dissolved in ethanol and allowed to slowly evaporate atambient conditions. A shoulder on a peak can be seen at about 24.7 ° 2θand a small doublet between about 26.2 and 26.6 ° 2θ are present in theexperimental pattern but not in the calculated pattern. Further, thisshoulder and double align with peaks in Form II. However, based on peakintensities, the Form II component is minor.

TABLE 1 Empirical formula C15 H14 N2 O4 Formula weight 286.28Temperature 120(2) K Wavelength 0.71073 Å Crystal system MonoclinicSpace group C2/c Unit cell dimensions a = 40.076(2) Å α = 90°. b =7.1979(4) Å β = 122.479(2)°. c = 22.2876(12) Å γ = 90°. Volume 5423.5(5)Å³ Z 16 Density (calculated) 1.402 g/cm³ Absorption coefficient 0.103mm⁻¹ F(000) 2400 Crystal size 0.34 × 0.14 × 0.12 mm³ Theta range fordata collection 1.83 to 31.00°. Index ranges −58 <= h <= 58, −10 <= k <=6, −20 <= 1 <= 32 Reflections collected 30156 Independent reflections8438 [R(int) = 0.0406] Completeness to theta = 31.00° 97.5% Absorptioncorrection None Max. and min. transmission 0.9877 and 0.9657 Refinementmethod Full-matrix least-squares on F² Data/restraints/parameters8438/0/403 Goodness-of-fit on F² 1.084 Final R indices [I > 2sigma(I)]R1 = 0.0537, wR2 = 0.1346 R indices (all data) R1 = 0.0887, wR2 = 0.1492Largest diff. peak and hole 0.506 and −0.257 e.Å⁻³

We claim:
 1. Form II of a 1:1 cocrystal of p-coumaric acid andnicotinamide.
 2. The cocrystal of claim 1 having an x-ray powderdiffraction pattern comprising a peak at about 26.3° 2θ.
 3. Thecocrystal of claim 2 wherein the x-ray powder diffraction patternfurther comprises two peaks between about 15.4 ° 2θ and 16.0 ° 2θ. 4.The cocrystal of claim 1 having a melting onset temperature of about158° C.
 5. The cocrystal of claim 1 having an x-ray powder diffractionpattern comprising a peak at about 26.3° 2θ and two peaks between about15.4 and 16.0 ° 2θ.
 6. The cocrystal of claim 5 having a melting onsettemperature of about 158° C.
 7. Form III of a 1:1 cocrystal ofp-coumaric acid and nicotinamide.
 8. The cocrystal of claim 7 having anx-ray powder diffraction pattern comprising a peak at about 25.8° 2θ. 9.The cocrystal of claim 8 wherein the x-ray powder diffraction patternfurther contains only one peak between about 15.4 ° 2θ and 16.0 ° 2θ.10. The cocrystal of claim 7 having a melting onset temperature of about160° C.
 11. The cocrystal of claim 7 having an x-ray powder diffractionpattern comprising a peak at about 25.8° 2θ and only one peak betweenabout 15.4 ° 2θ and 16.0 ° 2θ.
 12. The cocrystal of claim 11 having amelting onset temperature of about 160° C.
 13. A pharmaceuticalcomposition comprising at least one cocrystal of claim 1 and at leastone pharmaceutically acceptable carrier.
 14. The pharmaceuticalcomposition of claim 13 wherein at least one cocrystal is in apharmaceutically effective amount.
 15. A method of treating inflammationby administering to a patient in need thereof a pharmaceuticalcomposition of claim
 14. 16. A pharmaceutical composition comprising atleast one cocrystal of claim 7 and at least one pharmaceuticallyacceptable carrier.
 17. The pharmaceutical composition of claim 16wherein at least one cocrystal is in a pharmaceutically effectiveamount.
 18. A method of treating inflammation by administering to apatient in need thereof a pharmaceutical composition of claim 17.